Disallow prebuilt_root module type from setting Dsts property

...to prevent prebuilt_root module type from installing files in
arbitrary locations within the partition.

Test: m nothing --no-skip-soong-tests
Bug: 402903576
Change-Id: I6999c3256668bbe738a38abc4accc05e390511ba
diff --git a/fsgen/prebuilt_etc_modules_gen.go b/fsgen/prebuilt_etc_modules_gen.go
index 0adf7a1..df945b3 100644
--- a/fsgen/prebuilt_etc_modules_gen.go
+++ b/fsgen/prebuilt_etc_modules_gen.go
@@ -164,7 +164,6 @@
 	Ramdisk             *bool
 
 	Srcs []string
-	Dsts []string
 
 	No_full_install *bool
 
@@ -355,11 +354,14 @@
 				moduleFactory = etc.PrebuiltAnyFactory
 			}
 			modulePropsPtr.Srcs = srcBaseFiles
-			dsts := []string{}
+			dsts := proptools.NewConfigurable[[]string](nil, nil)
 			for _, installBaseFile := range installBaseFiles {
-				dsts = append(dsts, filepath.Join(relDestDirFromInstallDirBase, installBaseFile))
+				dsts.AppendSimpleValue([]string{filepath.Join(relDestDirFromInstallDirBase, installBaseFile)})
 			}
-			modulePropsPtr.Dsts = dsts
+
+			propsList = append(propsList, &etc.PrebuiltDstsProperties{
+				Dsts: dsts,
+			})
 		}
 
 		ctx.CreateModuleInDirectory(moduleFactory, srcDir, propsList...)